Optical properties and instrumental performance of thin gold films near the surface plasmon resonance

The optical properties of very thin gold films have been evaluated by Fresnel analysis, with optical boundary conditions pertaining to the surface plasmon resonance (SPR) at the gold-water interface. The experimental SPR characteristic was evaluated in the angular interrogation mode. Film morphology was characterized by high resolution transmission electron microscopy. The magnitude of the resonance, i.e., the SPR signal, sensitively depends on, and is affected by film thickness and morphology. A sharply defined thickness of 55 ± 5 nm is required, to achieve optimum SPR excitation conditions, and instrumental sensitivity. With decreasing film thickness, below 40 nm, the resonance angle starts to shift to larger values. A substantial increase of the intrinsic resonance broadening parameter is observed below 70 nm, associated with an increasingly asymmetric SPR line shape. A similar effect occurs in the presence of a very thin chromium adhesion layer. Surface roughness and film thickness modulations determine the experimentally observed line broadening parameter. Instrumental noise levels largely depend on accuracy and quality at which the resonance angle can be determined. Substantial improvement and instrumental sub-pixel resolution is achievable by optimum fitting routines, accounting for drastic noise reduction and improved instrumental sensitivity, up to two orders of magnitude over the inherent geometric sensor pixel resolution.     

Auger electron spectroscopy and electron energy loss spectroscopy studies of the formation of silicon nitride by implanting low energy nitrogen ions into silicon

Thin (d ? 10 nm) films of almost stoichiometric silicon nitride were prepared by implanting nitrogen ions with energies below 5 keV into silicon with subsequent thermal annealing. A combination of Auger electron spectroscopy (AES) and electron energy loss spectroscopy (ELS) was used to determine the chemical composition and to investigate the chemical bonding states of the thin films. The spectra are in good agreement with those obtained for Si₃N₄ produced by chemical vapour deposition. The use of AES and electron ELS allowed the stepwise formation of the SiN bonds to be investigated for the first time, and hence further information about the electronic structure of Si₃N₄ was obtained. Depth-concentration profiles for nitrogen are presented.     

A brief review of quantitative aspects of electron energy loss spectroscopy and imaging

Abstract

This review addresses a number of aspects of electron energy loss spectroscopy (EELS) for quantitative analysis, including: procedures for the quantification of EELS elemental analysis and mapping with an indication of the accuracies and detection sensitivities; procedures for the extraction of valence band electronic structures using low loss spectroscopy; and an outline of methods available for the quantitative determination of local valencies, coordinations, and bond lengths of atomic species using electron loss near edge and extended fine structures (ELNES and EXELFS). Additionally, a number of applications of quantitative EELS in spatially resolved studies of interfaces and defects are highlighted.     

Some problems of heat and mass exchange of a gas suspension with recuperative energy supply

The problem of heat exchange between a stream of a gas suspension and a third heat-transfer agent with recuperative energy supply is formulated and solved numerically.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 37, Ho. 4, pp. 649–656, October, 1979.     

Study of the Lorentz-Lorenz law and the energy loss of He ions in titanium oxide films

The optical constants, thicknesses and densities of thin titanium oxide films, deposited by electron beam evaporation, were measured. The variation of the refractive index with the density, of titanium oxide samples in the form of thin films (present work) and bulk crystalline form (data from the literature), was observed to follow the Lorentz-Lorenz law. The molecular electronic polarizability deduced from the law was close (within the uncertainty in the measurement) to the value reported in the literature. Rutherford backscattering spectroscopy and X-ray photoelectron spectroscopy studies were carried out on the thin films.     

Effects of Li and Fe doping on dielectric relaxation behavior in (Li,Fe)-doped NiO ceramics

High permittivity (Li, Fe)-doped NiO (LFNO) ceramics are prepared by a simple PVA sol–gel route and their dielectric properties are investigated as functions of temperature and frequency. It is found that the concentrations of Li and Fe have strong influences on the microstructure and dielectric properties of the LFNO ceramics. Two thermally activated dielectric relaxations are observed in the Li_0.05Fe_0.10Ni_0.85O ceramic sample with the activation energies of 0.448 and 0.574 eV for the high- and low-frequency relaxations, respectively. By using a complex impedance analysis, it is believed that the high-frequency relaxation is closely related to the transport properties inside the grains, and the low-frequency relaxation might be ascribed to the interfacial polarization at the interface layers of grain boundaries and/or NiFe₂O₄ secondary phase layers.     

Characterisation of nano-structured titanium and aluminium nitride coatings by indentation, transmission electron microscopy and electron energy loss spectroscopy

Titanium and aluminium nitride Ti_1 − xAl_xN films deposited by radiofrequency magnetron reactive sputtering onto steel substrate are examined by transmission electron microscopy over all the range of composition (x = 0, 0.5, 0.68, 0.86, 1). The deposition parameters are optimised in order to grow nitride films with low stress over all the composition range. Transmission electron microscopy cross-section images of Vickers indentation prints performed on that set of coatings show the evolution of their damage behaviour as increasing x Al content. Cubic Ti-rich nitrides consist of small grains clustered in rather large columns sliding along each other during indentation. Hexagonal Al-rich films grow in thinner columns which can be bent under the Vickers tip. Indentation tests carried out on TiN and AlN films are simulated using finite element modelling. Particular aspects of shear stresses and displacements in the coating/substrate are investigated. The growth mode and the nanostructure of two typical films, TiN and Ti_0.14Al_0.86N, are studied in detail by combining transmission electron microscopy cross-sections and plan views. Electron energy loss spectrum taken across Ti_0.14Al_0.86N film suggests that a part of nitrogen atoms is in cubic-like local environment though the lattice symmetry of Al-rich coatings is hexagonal. The poorly crystallised domains containing Ti and N atoms in cubic-like environment are obviously located in grain boundaries and afford protection of the coating against cracking.     

Quantitative analyses of oxidation states for cubic SrMnO(3) and orthorhombic SrMnO(2.5) with electron energy loss spectroscopy

The oxidation state of Mn in cubic SrMnO(3) and orthorhombic SrMnO(2.5) was investigated by electron energy loss (EEL) spectroscopy. Change in the oxidation state of Mn produced some spectral changes in the O-K edge as well as in the Mn-L(2,3) edge EEL spectra. This study demonstrated that the oxidation state of Mn and the amount of oxygen vacancies in cubic SrMnO(3) and orthorhombic SrMnO(2.5) could be quantified by analyzing the features of the O-K edge spectrum and the Mn L(3)∕L(2) ratio in the Mn-L(2,3) edge spectrum. Our quantitative analysis showed that the spectral changes in the Mn-L(2,3) edge were mainly caused by the oxidation state of Mn, whereas those in the O-K edge could be sensitive to both the oxidation state of Mn and to lattice distortions.     

Numerical investigation of gas species and energy separation in the Ranque-Hilsch vortex tube using real gas model

A three dimensional Computational Fluid Dynamics (CFD) model is used to investigate the phenomena of energy and species separation in a vortex tube (VT) with compressed air at normal atmospheric temperature and cryogenic temperature as the working fluid. In this work the NIST real gas model is used for the first time to accurately compute the thermodynamic and transport properties of air inside the VT. CFD simulations are carried out using the perfect gas law as well. The computed performance curves (hot and cold outlet temperatures versus hot outlet mass fraction) at normal atmospheric temperature obtained with both the real gas model and the perfect gas law are compared with the experimental results. The separation of air into its main components, i.e. oxygen and nitrogen is observed, although the separation effect is very small. The magnitudes of both the energy separation and the species separation at cryogenic temperature were found to be smaller than those at normal atmospheric temperature.     

A model for predicting transport velocity in gas fluidized-beds

This study improved the model that used the correlation of the particle entrainment rate to determine the transport velocity. It proposed the new absolute value of the local slope as the criterion of the model for locating the transport velocity in the relationship between dimensionless velocity (U/U_t) and the reciprocal of the entrainment rate (1/K_i¹⁺). It indicated that the criterion depended on properties of fluidized particles and increased with Archemedes number. The Archemedes number was modified by substituting the critical diameter, the maximum particle diameter at which the sum of the interparticle adhesion forces gave a dominant influence to the particle entrainment rate, for the diameter of particles in case that the mean diameter of particles was smaller than the critical diameter. A correlation was suggested to calculate the absolute value of the local slope at the transport velocity. The new model was successful covering the effect of particle properties in predicting the transport velocity.     

Ion-induced elongation of gold nanoparticles in silica by irradiation with Ag and Cu swift heavy ions: track radius and energy loss threshold

Systematic investigations of the energy loss threshold above which the irradiation-induced elongation of spherical Au nanoparticles occurs are reported. Silica films containing Au nanoparticles with average diameters of 15-80 nm embedded within a single plane were irradiated with 12-54 MeV Ag and 10-45 MeV Cu ions at 300 K and at normal incidence. We demonstrate that the efficiency of the ion-induced nanoparticle elongation increases linearly with the electronic energy transferred per ion track length unit from the energetic ions to the silica film. Ion beam shaping occurs above a threshold value of the specific electronic energy transfer. Three relevant regions are identified with respect to the original size of the Au nanoparticles. For 15 and 30 nm diameter particles, elongation occurs for electronic stopping power larger than 3.5 keV nm(-1). For Au nanoparticles with 40-50 nm diameter an electronic stopping power above 5.5 keV nm(-1) is required for elongation to be observed. Elongation of Au nanoparticles with 80 nm diameter is observed for electronic stopping between ～ 7-8 keV nm(-1). For all combinations of ions and energies, the ion track temperature profiles are calculated within the framework of the thermal spike model. The correlation between experimental results and simulated data indicates a thermal origin of the increase in the elongation rate with increasing the track diameter.     

A DRBEM model for harbor oscillation with the effect of energy dissipation

Abstract

In this study, the numerical scheme of dual reciprocity boundary element method (DRBEM) is adopted to investigate the resonant problem in a harbor while considering the effect of energy dissipation. The numerical model employed the mild slope equation as a basic equation. To avoid complicated procedures for solving the equation, DRBEM is used to improve numerical efficiency. Computation results are compared with the existing experimental data and other theoretical results. It shows that the present model is valid and effective to solve the harbor oscillation problem.     

Transmission electron microscopy/electron energy loss spectroscopy measurements and ab initio calculation of local magnetic moments at nickel grain boundaries

We have determined local magnetic moments at nickel grain boundaries using a transmission electron microscopy/electron energy loss spectroscopy method assuming that the magnetic moment of Ni atoms is a linear function of the L₃/L₂ (white-line ratio) in the energy loss spectrum. The average magnetic moment measured in the grain interior was 0.55 μ_B, which agrees well with the calculated magnetic moment of pure nickel (0.62 μ_B). The local magnetic moments at the grain boundaries increased up to approximately 1.0 μ_B as the mis-orientation angle increased, and showed a maximum around 50°. The respective enhancement of local magnetic moments at the Σ5 (0.63 μ_B) and random (0.90 μ_B) grain boundaries in pure nickel was approximately 14 and 64% of the grain interior. In contrast, the average local magnetic moment at the (111) Σ3 grain boundary was found to be 0.55 μ_B and almost the same as that of the grain interior. These results are in good agreement with available ab initio calculations.     

A stochastic multi-objective optimization decision model for energy facility allocation: a case of liquefied petroleum gas station

Clean Technologies and Environmental Policy - To mitigate air pollution problem, the government has been planning to build more liquefied petroleum gas stations to motivate drivers to use liquefied...     

Evidence of energy transfer among Nd ions in Nd:YAG driven by a mixture of exchange and multipolar interactions

The non-radiative energy transfer between Nd ions in Nd:YAG is investigated through high time-resolution fluorescence measurements of the level of Nd. Our experimental data suggests that a strong short-range interaction, i.e., exchange interaction, contributes to the energy transfer process between Nd ions at early times. In addition to it, our Monte Carlo simulations predict a multipolar mixture of interactions, that is, dipole–dipole, dipole–quadrupole, quadrupole–quadrupole and exchange interactions. This result is compared with a similar measurement and analysis for the Nd, Er, Cr:YAG luminescent system previously reported.     

A model for foamed cementing of oil and gas wells

We present a two-dimensional model of the primary cementing process for foamed cement slurries. Foamed cement slurries have a number of claimed advantages, but also have a pressure-dependent density and rheology. The rheology is hard to quantify fully over all ranges of foam quality, which compromises the accuracy of models. The density variation is due to expansion/compression of the gas phase along the well, caused by variations in the static pressure. We show that in the absence of careful control, buoyancy-driven instabilities can result in the annulus, as the foamed slurry expands and the density drops below that of the displaced drilling mud. These instabilities appear to be of a classic porous media/Hele-Shaw cell fingering type, triggered by a threshold unstable density difference. We show that these instabilities are amplified by wellbore eccentricity, occurring lower in the well than in a concentric annulus. Our results question the safe usage of foamed cements in primary cementing.     

Influence of the gas composition on the electron transport coefficients in helium-based gas mixtures

For several helium–isobutane and helium–methane gas mixtures the drift velocity and the longitudinal and transversal diffusion coefficients have been measured with a time of flight method using single-drift electrons. The influence of the hydrocarbon, water and nitrogen content in the gas mixture on the transport coefficients was studied in detail for concentrations typical for the operation of drift chambers.     

A mathematical model and its analytical solution for slow depressurization of a gas-filled vessel

The operation safety of depressurizing a high-pressure gas-filled vessel is of crucial importance in petroleum, chemical and biological processing industries. The present study describes a simple model of a slow depressurization process and derives its analytical solution in a recurrence form. This analytical solution is expected to be useful for engineering applications and for the assessment of either detailed numerical simulations or experimental data.     

Synthesis, characterization and effect of low energy Ar ion irradiation on gadolinium oxide nanoparticles

In this work, we report on the surfactant assisted synthesis of gadolinium oxide (Gd₂O₃) nanoparticles and their characterization through various microscopic and spectroscopic tools. Exhibiting a monoclinic phase, the nanoscale Gd₂O₃ particles are believed to be comprising of crystallites with an average size of ∼3.2 nm, as revealed from the X-ray diffraction analysis. The transmission electron microscopy has predicted a particle size of ∼9 nm and an interplanar spacing of ∼0.28 nm. Fourier transform infrared spectroscopy studies show that Gd-O inplane vibrations at 536.8 and 413.3 cm⁻¹ were more prominent for 80-keV Ar-ion irradiated Gd₂O₃ nanosystem than unirradiated system. The photoluminescence (PL) spectra of irradiated specimen have revealed an improvement in the symmetry factor owing to significant enhancement of surface-trap emission, compared to the band-edge counterpart. Irradiation induced creation of point defects (oxygen vacancies) were predicted both from PL and electron paramagnetic resonance (EPR) studies. Further, the Raman spectra of the irradiated sample have exhibited notable vibrational features along with the evolution of a new peak at ∼202 cm⁻¹. This can be ascribed to an additional Raman active vibrational response owing to considerable modification of the nanostructure surface as a result of ion bombardment. Probing nanoscale defects through prime spectroscopy tools would find a new avenue for precise tuning of physical properties with generation and annihilation of defects.     

A model of valence electron structure for embrittlement of TiAl

In this paper, the valence electron structure and embrittlement of TiAl are studied theoretically based on the empirical electron theory (EET). From the viewpoint of the EET, a model for the space topographic distribution of valence electron structure is proposed. This model can be used to simply explain the embrittlement of TiAl and could be extended to other intermetallic compounds.